Pericardial fat and atrial conduction abnormalities in the Multiethnic Study of Atherosclerosis (MESA).

Pericardial fat (Pfat) overlies the cardiac surface including atria and their inter- and intra-conduction system. Through its local inflammatory effects, Pfat may predispose to atrial abnormalities that could be detected as changes in P-wave morphology in the 12-lead electrocardiogram (ECG). We evaluated the association between Pfat and ECG measurements of P wave and PR interval (referred to as P-wave indexes): PR duration (PR-dur), P-wave duration (P-dur), and P-wave terminal force (P-term), in the Multiethnic Study of Atherosclerosis (MESA). Participants with available Pfat measured by computed tomography (CT) and P-wave indexes measured by ECG were included (N = 996). Differences in P-wave indexes per 1 standard deviation difference in Pfat were tested in unadjusted linear regression analysis first, then adjusted for demographics (age, sex, and ethnicity), and further adjusted for measures of adiposity (BMI or waist circumference (WC)), or cardiovascular risk factors (hypertension (HTN), diabetes, and smoking). All P-wave indexes were significantly associated with Pfat in unadjusted analyses (regression-coefficient (β) (95% CI): PR-dur (ms) 2.53 (1.02, 4.04), P-dur (ms) 2.59 (1.84, 3.35), P-term (µV·s) 0.25 (0.13, 0.36)). After demographics adjustment, P-dur (1.68 (0.87, 2.49)) and P-term (0.16 (0.04,0.28)), but not PR-dur (1.11 (-0.52, 2.74)) were associated with Pfat. No associations were significant after adjustment for BMI, WC, or cardiovascular disease (CVD) risk factors. BMI and WC, separately, were significantly associated with P-wave indexes in all models, including those that included Pfat as a covariate. BMI, but not WC, was associated with P-wave indexes when the two were entered into the same model. In conclusion, Pfat is associated with P-wave indexes, but not after adjusting for measures of adiposity or CVD risk factors. Among Pfat, BMI and WC, BMI had the most robust association with P-wave indexes. These findings raise doubts about potential local effects of Pfat on atrial electrophysiology and morphology.